Re: [Xen-devel] [PATCH RFC 00/39] x86/KVM: Xen HVM guest support

[Juergen Gross]

On 21/02/2019 00:39, Marek Marczykowski-GÃrecki wrote:
> On Wed, Feb 20, 2019 at 08:15:30PM +0000, Joao Martins wrote:
>>  2. PV Driver support (patches 17 - 39)
>>
>>  We start by redirecting hypercalls from the backend to routines
>>  which emulate the behaviour that PV backends expect i.e. grant
>>  table and interdomain events. Next, we add support for late
>>  initialization of xenbus, followed by implementing
>>  frontend/backend communication mechanisms (i.e. grant tables and
>>  interdomain event channels). Finally, introduce xen-shim.ko,
>>  which will setup a limited Xen environment. This uses the added
>>  functionality of Xen specific shared memory (grant tables) and
>>  notifications (event channels).
> 
> Does it mean backends could be run in another guest, similarly as on
> real Xen? AFAIK virtio doesn't allow that as virtio backends need
> arbitrary write access to guest memory. But grant tables provide enough
> abstraction to do that safely.

As long as the grant table emulation in xen-shim isn't just a wrapper to
"normal" KVM guest memory access.

I guess the xen-shim implementation doesn't support the same kind of
guest memory isolation as Xen does?


Juergen